Light-Footed Clapper Rail Management and Population Assessment, 1993

State of California The Resource Agency Department of Fish and Game Wildlife Management Division LIGHT-FOOTED CLAPPER RAIL MANAGEMENT AND POPULATION ASSESSMENT, 1993 by Richard Zembal Nongame Bird and Mammal Program Report, 94-6 FINAL REPORT TO California Department of Fish and Game 1416 Ninth Street Sacramento, CA 95814 CONTRACT FG2327 (FY 92/93) Partially Supported by Section 6 Federal Grant-in-Aid Funding for Endangered Species, California, EW92, X-l LIGHT-FOOTED CLAPPER RAIL MANAGEMENT AND POPULATION ASSESSMENT, 1993 CONTRACTOR California State University, Long Beach Foundation Long Beach, California 90840 PROJECT ADMINISTRATOR Dr. Charles T. Collins Department of Biology California State University Long Beach, CA 90840 AUTHOR AND PRINCIPAL INVESTIGATOR Richard Zembal Research Associate State of California The Resources Agency Department of Fish and Game Wildlife Management Division LIGHT-FOOTED CLAPPER RAIL CENSUS AND STUDY, 1993 by Richard Zembal Research Associate, Biology Department California State University Long Beach, CA 90840 ABSTRACT The fourteenth consecutive annual census of the endangered light-footed clapper rail (Rallus longirostris levipes) was conducted by call counts throughout the bird's range in California, 3 March - 15 April 1993. There were 300 pairs of clapper rails exhibiting breeding behavior in 13 marshes, a 9% increase over 1992. One hundred and forty-two pairs, or 47.3% of the state total, were detected at Upper Newport Bay. The subpopulations in the Tijuana Marsh National Wildlife Refuge (NWR), Seal Beach NWR, and Upper Newport Bay totalled 270 pairs, or 90% of the California population. Most of the subpopulations are small and face serious problems that should be dealt with through increased management and the provision of additional habitat or they will be lost. There is little security in the continued existence of the light-footed clapper rail without several large viable population centers. High tide counts were continued on the Seal Beach NWR and 143 clapper rails were sighted in October. This count demonstrated the maintenance for a second year of high clapper rail numbers on the refuge. Effective control of nonnative red foxes (Vulpes) allowed the manifestation of the clapper rail's high reproductive potential and is leading to the recovery of this important subpopulation. With proper management, rails could establish on the adjacent State Ecological Reserve at Bolsa Chica. Ten trapping sessions at Upper Newport Bay with 13 - 19 drop-door traps and 518 trap-hours, resulted in the capture and unique color-banding of 16 more clapper rails and 1 recapture. There were 18 resightings of 7 banded rails. The average movement Zembal, R. 1994. Light-footed clapper rail management and population assessment, 1993. Contract Report to the Calif. Dep. Fish and Game. Wildl. Manage. Div., Nongame Bird and Mammal Section Rep. 94-06. 32 pp. detected of these rails was 85 meters. The largest spread of detection points for any rail was of 437 meters. This rail was a first-year bird that moved to a new section of marsh and then established itself in one locale where it was observed repeatedly. The longest time span between banding and resighting of any one of the 179 rails banded since March 1981 has been 5 years. Six of the 7 resighted rails were first banded in 1992, the other in 1993. Banding success over the 12 years of banding is compared, and resightings of banded rails are summarized for the 11 banding sessions accomplished 1981 - 1992. Over half of the 163 rails banded during this period were reencountered and 12.7% of the 157 rails captured in drop-door traps were recaptured in them, 1 hour to 48.3 months later. Seventy-nine clapper rail nests were found on the 100 rafts made available in the Seal Beach NWR. Fifty-two of the nests held 73 clutches of eggs and there were at least 9 additional brood nests. Recruitment was very high due to decreased predation. Hatching success was 86% for initial attempts and 60% for renests. The 15 nesting rafts deployed at the Kendall-Frost Reserve contained 13 clapper rail nests but only 5 clutches of eggs. Hatching success was 100% but there is additional evidence that predation is a major problem at Kendall-Frost. More rafts are recommended for both these wetlands and several others. Twenty-six rafts were placed in the Sweetwater Marsh NWR too late in the spring to expect any use. In spite of the lateness, two of the rafts were nested upon successfully by clapper rails. A nesting raft project was also initiated on Middle Island in Upper Newport Bay. The rafts were placed too late for nesting but clapper rails did use them for cover during a high tide. Continued coyote (Canis latrans) use of the wetlands at Seal Beach NWR and Carpinteria Marsh was documented during predator monitoring activities. Raptor watches at Upper Newport Bay quantified bird of prey activity and interactions with marsh birds. Activities and abundance of 10 diurnal species were summarized for 10 winter sessions. INTRODUCTION The light-footed clapper rail (Rallus longirostris levipes) is a State and federally listed endangered species that is resident in coastal wetlands in southern California and northern Baja, California, Mexico. Loss and degradation of habitat threaten the continued existence of this subspecies, although management efforts now offer some promise of recovery. The California population of this endangered bird was up to 300 pairs in 1993, the largest number detected breeding in one year since monitoring and study began in 1979. Herein are reported the results of the fifteenth year of survey, study, and management efforts. STUDY AREAS The marshes occupied recently by light-footed clapper rails were described by the U.S. Fish and Wildlife Service (1985) and Zembal and Massey (1981). The two principle study areas were the Seal Beach National Wildlife Refuge (NWR) and Upper Newport Bay, both in Orange County. The Seal Beach NWR covers 369 ha (911 acres) of the 2,024 ha (5,000 acre) Seal Beach Naval Weapons Station. About 299 ha (739 acres) of the refuge lands are subject to regular inundation by the tides. There are about 229 ha (565 acres) of salt marsh vegetation, 24 ha (60 acres) of mudflats that are exposed daily, and 46 ha (114 acres) of channel and open water. The wetlands are fully tidal, with a range of about - 0.5 m (1.7 ft) to + 2.2 m (7.2 ft) MLLW, and very productive with a high diversity and abundance of wildlife. Upper Newport Bay is an Ecological Reserve of the California Department of Fish and Game (Department), located approximately 22 km (13.7 mi) downcoast of the Seal Beach NWR. Approximately 304 ha (750 acres) are fully tidal, including 105 ha (260 acres) of marsh. The bay is flanked by bluffs 9 - 18 m (30 - 59 ft) high and surrounded by houses and roads. There are approximately 100 ha (247 acres) of shrublands remaining undeveloped on the edge of the wetlands and two local drainages with some cover along them coursing into the bay. METHODS Call Counts The fourteenth consecutive annual census of light-footed clapper rails in California was conducted 3 March - 15 April 1993. Thirty-six coastal wetlands were surveyed by mapping territorial pairs based on their calls (Zembal and Massey 1981, 1985; Zembal 1992). In the 4 marshes with abundant clapper rails, mapping spontaneous calls was the prevalent technique. In marshes with few rails and along long, narrow strips of habitat, playbacks of taped "clappering" calls were used sparingly to elicit responses. In a few years at several marshes, and each year at Tijuana Marsh National Wildlife Refuge (NWR), enough observers were stationed to be within potential hearing range of any calling rail over the entire marsh on a single evening. Most of the marshes are surveyed by a single observer visiting discrete patches of habitat on consecutive evenings until all of the habitat has been censused. Most of the observations for all years were those of three observers, and since 1985, all but a few of the southern San Diego County wetlands were surveyed by Zembal. The more movement required of an observer during a survey, the more likely that breeding, but infrequently calling, rails were missed. Calling frequency and the detection of calls were influenced by observer's hearing ability and experience with the calls, the stage of breeding of individual pairs, rail density, and weather conditions (Zembal and Massey 1987). Many surveys attempted on stormy, windy days had to be repeated. If calling frequency was high with many rounds issuing from the marsh as adjacent pairs responded to one another, it was possible to map the rails well and move on to survey more marsh. Under usual circumstances approximately 20 ha (50 acres) of marsh could be adequately covered during a single survey. Early morning and late evening surveys were comparable, although evening calling by the rails was more intense and often ended with one or more flurries (Zembal et al 1989). Surveys were usually conducted in the 2 hrs before dark, but some were done at first light to about 2 hrs after sunrise. The playback of a taped "clappering" call appeared to be responded to by the rails as if it were a living pair calling nearby. However, work done with Yuma clapper rails (Rallus longirostris yumanensis) suggests strongly that those closely related rails can become conditioned to the tape if it is used excessively (B. Eddleman, pers. comm.). During prime calling times in the evening or early morning, a playback sometimes elicited a response or even a round of calling. However, there were sometimes no vocal responses to the tape. If played at a time of day when the rails are not particularly prone to call, the only response likely to be solicited was that of the territorial pair intruded upon.

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